Process for preparing bulked yarns



Jan. 11, 1966 D. GIUDICI ETAL 3,228,180

PROCESS FOR PREPARING BULKED YARNS Filed May 6, 1965 N IO I v w I United States Patent PROCESS FOR PREPARING BULKED YARNS Davide Giudici, Via Vassena 3, Sala al Barro, Como, Italy, and Mario Roselli, Viale Vittorio, Veneto 18, Milan, Italy Filed May 6, 1963, Ser. No. 278,190 Claims priority, applicationltaly, May 11, 1962, 9,459/62 1 Claim. (Cl. 57-157) This invention relates to a process for producing bulked yarns and to an apparatus for performing the process.

The term bulked yarn, of course, covers a yarn which has been given special treatments (heating, false twisting, drawing and so on) to make it suitable for particular purposes (handkerchiefs, scarfs, ski pants, knitted outer wear, knitted underwear, furnishing fabrics and so on). Yarn for bulking is usually a synthetic although the process can be used with some natural fibres, such as silk.

It is an object of this invention to provide a simple low-cost process for producing different kinds of bulked yarn.

The invention also relates to an apparatus for performing the process.

In the bulked yarn production process according to the invention, the yarn, having previously been given a false twist elasticising treatment, is cold drawn or slackened substantially at ambient temperature and then, in a continuous production cycle, is given hot drawing or slackening treatment. This consecutive cold and hot treatment leads to a surprising increase in the range of fibres which can be given bulking treatment. For instance, silk and some polyvinylchloride and polypropylene resins can be bulked in this way. The process is also of use with uneven yarns, such as slivers.

The reason for the increased range is that the two phases of cold treatment and hot treatment provide an advantageous way for varying the percentage of cold and hot drawing or slackening. A result of such percentage being variable is that different kinds of yarn can be provided. There are two main categories of yarn which can be produced. There are yarns having a defined dimensional stability, for instance, for use in knitting and needle work. The other kind is effect yarns, that is, yarns which develop their characteristics when at a later stage of processing they are given thermal or mechanical stressing (mesh weave, but mainly finishing).

At present it is impossible to give a scientific explanation for the events which occur in the yarn as a result of the two treatments, but it is thought that the molecular structure of the yarn changes continuously, more particularly during the cold drawing or slackening phase previous to the hot phase. The reason for this is that, if the yarn is pulled during the cold treatment, the molecular chains (which in the pulled synthetic fibres are initially disposed parallel to the fibre axis) which have undergone a change in their structure, since the molecular orientation has been changed by the combined effects of twisting and heat during the previous false twist elasticisation treatment, are forced to abandon the structure taken up during such treatment, lose elasticity, which is dependent upon the changed molecular orientation, and reorientate themselves parallel to the fibre axis. The new molecular structure thus formed can be fixed in the conditions in which it was obtained if the tension is maintained during the consecutive passage of the yarn through an oven at an appropriately high temperature, or in conditions different from the cold treatment conditions, as a reaction thereto in the event of the yarn being left free to slacken during its passage through the oven.

If, on the other hand, the yarn is left free to slacken cold, the yarn tends to shorten as a result of the false twisting treatment, as a result of the modification to its molecular orientation, which may explain its action when it is not constrained. As it shortens, the yarn count increases and, to a limit, so does the yarn bulk. The yarn, with its dimensions artificially varied and controlled in this way, then enters the heat treatment oven and is fixed to the required dimensions, with complete or partial slackening or even with drawing if the treated yarn is required to react to a desired mechanical stressing, and at temperatures equal to or above the temperatures of the first oven, in cases where the yarn is required to be finally stabilised with this cycle of working, or at lower temperatures if the yarn is to react to desired heat finishings.

The process according to the invention and the apparatus for performing the process will be described hereinafter in greater detail by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic front elevation in fragmentary form of an apparatus for performing the bulking process according to the invention, only that part of the apparatus which is of interest for this invention being shown, and

FIGURE 2 is a purely diagrammatic view showing the same machine as is shown in FIGURE 1 but in side elevation and with some parts omitted to facilitate an understanding of the invention.

A yarn-bulking apparatus is completed by a base bearing some form of pay-off bobbin for the raw yarn and a take-up bobbin for the bulked yarn. As can be seen in FIGURES 1 and 2, the apparatus comprises a number of treatment groups (two such groups are shown in FIG- URE 1) each formed by a pair of rollers 1 (in each pair of rollers, one roller is driving and the other driven), a first oven 2, a rotating twisting spindle diagrammatically indicated by the reference 3, a second roller pair 4, a third roller pair 5, an oven 6 and a fourth roller pair 7.

This apparatus operates as follows:

Raw yarn 8 from some form of pay-off device (not shown) passes between the rollers 1 and thence into the oven 2 and to the rotating twisting spindle 3 and so to the rollers 4. That part of the procedure which extends as far as the rollers 4 serves merely to provide an elasticised yarn by means of the continuous false twisting method. This part of the cycle is conventional in the preparation of elasticised yarns and does not form part of this invention and so will not be described in any greater detail.

The elasticised yarn leaving the rollers 4 passes to atmosphere, is taken up by the rollers 5, then passes through the second oven 6 and onto the rollers 7. On its path between the rollers 4 and the rollers 5, the elasticised yarn experiences a cold drawing or a cold slackening at ambient temperature; thereafter, the yarn is given heat treatment in the oven 6 to fix the new structure produced in the yarn while the same was travelling between the rollers 4 and the rollers 5; simultaneously, the yarn is given further drawing or slackening between the rollers 5 and the rollers 7. The bulked yarn 8 leaving the rollers 7 is taken up on a take-up bobbin (not shown) in the form of bulked yarn.

Since the process according to the invention is of use with a very large number of yarns, it is substantially impossible to give percentages of drawing or slackening to be used in the cold and hot treatments nor to state any temperatures for the heat treatments. The engineer in the art can determine these quantities for each particular case in the light of immediate requirements. The important thing is that the engineer in the art is provided with means for increasing the range of yarns which can be bulked and for producing bulked yarns of any kind 'as a result of the possibility of varying yarn structure in two consecutive drawing or slackening treatments, the first such treatment being cold or at ambient temperature and the second such treatment being hot.

The apparatus according to the invention for giving this double treatment is very simple since in it the two ovens, the first for the conventional false twisting elasticising heat treatment and the second for the heat treatment following the cold treatment, are combined to form a single member; cold treatment is given to the yarn passing over the path between the two heat treatments, that is, the path between the rollers 4 and the rollers 5.

The apparatus described can be controlled in a variety of ways. The speed of the rollers 5 can be varied relatively to the speed of the rollers 4. The speed of the rollers 7 can be varied relatively to the speed of the rollers 5. The temperature of the second oven 6 can be varied relatively to the temperature of the first oven 2. All these control steps can be performed using means known to the engineers in the art and so will not be further described.

Although only one embodiment of this invention has been hereinbefore described, the same can, of course, be varied and' modified in many ways without departing from the scope of the invention.

We claim:

A process for preparing bulked yarn from raw yarn which comprises, heating and false twisting the raw yarn to produce an elasticised yarn, then cold stretching the elasticised yarn at ambient temperature, and finally continuously drawing and stretching the yarn While subjecting the yarn to heat.

References Cited by the Examiner FOREIGN PATENTS 166,208 12/ 1955 Australia.

870,175 6/ 1961 Great Britain. 876,104 8/1961 Great Britain. 883,604 12/ 1961 Great Britain.

MERVIN STEIN, Primary Examiner.

DONALD W. PARKER, Examiner. 

